The present disclosure relates to a semiconductor memory device, and more particularly, to an input/output line sense amplifier configured to increase power efficiency of a semiconductor memory device by reducing an operating current.
Data input/output (I/O) lines are used for data transmission in a semiconductor memory device. An output signal of a bit line sense amplifier (BLSA) in a memory cell area (or core area) is transmitted to a global I/O line (GIO) via a local I/O line (LIO). In general, the global I/O line is globally disposed over a plurality of banks, and transmits data between a data I/O pad and a memory cell area.
A circuit is required for data transmission between the global I/O line and the local I/O line. In the case of a dynamic random access memory (DRAM), an I/O line sense amplifier (IOSA) is used in a read operation to amplify data carried on the local I/O line and transfer the amplified data to the global I/O line, and a write driver (WDRV) is used in a write operation to amplify data carried on the global I/O line and transfer the amplified data to the local I/O line.
Conventional I/O line sense amplifiers may be divided into a one-stage amplification type and a two-stage amplification type. First, the one-stage application type I/O line sense amplifier has a simple circuit configuration, which contributes to decreasing current consumption. However, since an offset characteristic of an input signal is deteriorated, a potential difference between data carried on local I/O lines (LIO and LIOB) must be high enough to sufficiently amplify the data and transmit the amplified data to a global I/O line. To this end, it is necessary to delay an enabling period of a strobe signal for driving the I/O line sense amplifier by a predetermined time, but in this case, a column address access time (tAA) undesirably increases.
The two-stage application type I/O line sense amplifier amplifies data of the local I/O lines (LIO and LIOB) by two stages. Amplification operations of the two stages are sequentially driven by separate strobe signals, thereby improving offset characteristics of an input signal. Thus, even if the potential difference between data of the local I/O lines (LIO and LIOB) is small, the data can be sufficiently amplified and then transmitted to the global I/O line.